There are some rivalries — those ferocious cross-town antagonisms of Istanbul and Cairo, say, Athens and Rome, Belgrade and Tehran, or the multifarious, volatile Latin American clásicos and superclásicos — that are hewn for the ages, it would seem: a self-perpetuating, endlessly renovated symbiotic loathing in which each new supporter is compelled, as a kind of initiatory sine qua non, to adopt a bone-deep, acid-sweat hatred of the Other Lot. Now, while a modicum of intellectual modesty and smidgeon of philosophical rigour ought to preclude us from asserting with absolute certainty that these tête-à-têtes are, despite appearances, fixed and eternal (yes, even the Auld Firm), the fact that they rumble forward at glacial speed — nourished by an animosity so viscous and seemingly implacable that fans on both sides of the divide never escape the gravitational pull of their compulsory mutual abhorrence — indeed creates the sense of a de facto permanence from which the supporters henceforth appear to derive their rigid identity. I might not always be sure of what I'm for, exactly (because beneath the Holy Shirt we seem ever to mutate), but I know damn well what I'm against… 

Then there are others, lacking the fetid cheek-by-jowl antipathy of the metropolitan derbies, going by way of personalities rather than institutions and thus less durable, but that nevertheless attain, for a period, an intensity every bit as vehement and consumptive as those seemingly primordial antagonisms before ebbing away. In West Germany in the late 1960s and early 1970s, for instance, Borussia Mönchengladbach and Bayern Munich were fervid adversaries despite possessing between them most of the national team, while the same period in England saw bloodshed every time the Chelsea of 'Chopper' Harris locked horns with Don Revie's notoriously nefarious Leeds team. Indeed, the 1970 FA Cup final replay, watched by an incredible 28 million people, the second highest figure ever in the UK for a sports broadcast (eclipsed by the 1966 World Cup final alone), was arguably the most savage football match seen in Britain. When reviewed by David Elleray in 1995 through the lens of contemporary refereeing standards, he concluded that Leeds would have incurred seven bookings and three dismissals (Johnny Giles, Billy Bremner and Jack Charlton), while Chelsea deserved 13 yellows, including three each for Harris, Dave Webb and Charlie Cooke. As it was, so lenient was Eric Jennings, in his swansong as a referee, that only Chelsea's Ian Hutchinson saw yellow. 

A similarly foul and fierce yet ultimately temporary rivalry emerged during the early 1980s in Spain — that heterogeneous nation of somewhat precarious unity and internecine squabbles (always, until recently, offered as the fundamental cause of their failings in tournament football, of course) in which the extraordinarily tenacious cultural and historical roots of Barcelona's face-offs with Real Madrid have engendered the mightiest oak of a feud (one whose acrimony seems to have been ratcheted up still further by José Mourinho's pantomime villain shtick and the fact that there are no other serious top-dog candidates, the twin titans' financial power creating a positive feedback loop continually reinforcing their hegemonic duopoly). However, despite the Barça-Real antipathy, for a short time an enmity every bit as spiteful settled between two of the country's most potent institutional symbols of nationalism, both beacons of the autonomous regional identities emerging groggily from under the jackboots of Falangist Spain after Franco's death in 1975. In the blaugrana corner, there was the Catalanism embodied by FC Barcelona (self-avowedly més que un club, which tended to express itself and any hankerings for independence through comparatively moderate and mature assertions of its economic power and cultural advancement, the extrovert city of Barcelona long having prided itself on being the habitual sluice through which vanguard artistic, philosophical and scientific currents arrived from elsewhere in Europe. In the rojiblanco corner stood the standard bearers of Basque identity, Athletic of Bilbao, the only club aside from Barça and Real never to have been relegated from the Spanish top flight, a club whose reserves, Bilbao Athletic, often pull 10,000 spectators from a city that Phil Ball says "smells of football" — a throbbing industrial Glasgow to Barcelona's well-heeled, sophisticated Edinburgh.

Given that early-eighties Spain was still at the dawn of its tentative transition to democracy, one could be forgiven for assuming that Franco's assault on indigenous Catalan and Basque culture might have united these two clubs against the 'imperial' Real Madrid, occasional propaganda tool of the ultra-centralist Generalísimo (who of course invited the Luftwaffe's Condor Legion to bombard the symbolic cradle of Basque culture, Gernika, on 26 April 1937). However, for a short time their rivalry — fructified as much by specific personalities involved as by geography or history — really did surpass in fervour el clásico's historically sedimented enmity. And at the heart of it all were two men more than familiar to students of the sport's annals of infamy… 

Although the club has distinctly British roots — a fact borne out by its name (Athletic not Atlético although Franco did insist on the Spanish orthography, as indeed Barça were obliged to call themselves CF Barcelona, rather than FC) — it has nevertheless fielded an all-Basque team since 1912, which remains the case to this day (the current central defender Fernando Amorebieta plays for Venezuela, the country of his birth, but was raised in the Basque Country, where he has lived since he was two years old, while both of his parents are Basques, too, who simply happened to be working in Venezuela in the mid-eighties). So, this year marks a centenary without any Spaniards, let alone 'proper' foreigners in the Athletic ranks, unlike their neighbours from San Sebastián, Real Sociedad, who relaxed this rule in 1989 with the arrival of John Aldridge and then in 2001, signed a first non-Basque Spaniard when Boris joined from Real Oviedo. The whole question of the codification of 'Basqueness' is a complex one; however, if it is not, strictly speaking, wholly a question of birth, parentage, or upbringing, then neither is it entirely an ethnic or racial matter, since the criteria have long stretched to include maketos (non-Basque speaking immigrants), while in 2011 Jonás Ramalho became the first black player to represent the club. At any rate, as Sid Lowe has pointed out, "the policy has never been written down — to do so might even be illegal — and over the years it has undergone changes in interpretation, shifting with society, policy-makers and presidents." 

Whatever the precise criteria of Basqueness, and there is bound to be some vagueness for a stateless nation, there is a conspicuous sense of cultural uniqueness across the Basque homeland (Euskal Herria) — which straddles the French border. While a good deal of their historical self-esteem is drawn from the fact that they were never subject to feudalism and have always been a people of individual smallholders based on the inalienable basseri as the basic social unit, the present feeling of vasquismo is of course in large part anchored by the language, euskara, which, famously, is unrelated to all modern European tongues and thus continues to confound philologists and historians of linguistics. 

Howsoever dynamic and difficult to define it may be, Basques clearly feel a sense of separateness. When that has been challenged, the extreme end of the spectrum has turned to terrorism: ETA, the paramilitary Basque nationalist group, is officially held responsible for 829 assassinations since the early 1960s, including, in 1973, the car-bomb that killed the Spanish Prime Minister Admiral Luis Carrero Blanco. That event that gave rise to a somewhat grisly ditty among football-going Basque nationalists that contained the refrain, "He flew, he flew," a reference to his vehicle being so heavily dynamited that it actually came to rest on the roof of a nearby building. 

There is also a more moderate face to Basque pride: a distinctly passionate and proud footballing culture, one whose members flock, come rain or shine (and it is very often shrouded in a billowing Atlantic rain up there), to the pulsating, steep-sided San Mamés stadium, the country's first purpose-built footballing amphitheatre, widely and affectionately known as La Catedral . And the near-40,000 bilbaínos who congregate there come in particular to see those Basque players forged in the fabled cantera ('quarry'), a mine so rich that it has provided more Spain internationals than any other club save Real Madrid, and has brought eight league titles, a self-sufficiency and history of achievement that is the source of no little local satisfaction. Indeed, as the chant has it: "Con cantera y afición, no hace falta importación…" ("With cantera and support, we need not import").

Among the strongest teams ever seen at San Mamés — literally, for they were an overtly rugged, muscular side — was the one assembled by Javier Clemente, an ex-player whose career had been curtailed by serious injury and who took up office in the summer of 1981 after an apprenticeship served first at the local sides Getxo and Biskonia, then Athletic's reserves. The truculent, chain-smoking, often foul-mouthed Clemente — who would go on to coach the Spain national team from 1992 to 1998, arguably the height of Spain's dark-horse fetlock-pulling — was not exactly a coach renowned for his teams' sparkling football; indeed, he is widely credited with having coined the term tiki-taka; not in admiration, it should be said, but pejoratively, a typically brusque and dismissive depiction of what he considered pointless or aimless passing for its own sake. As Sid Lowe has illustrated, in Spain the feisty Basque will "forever be associated with the phrase 'patapún y p'arriba' — 'bish-bosh, up it goes', a kind of Spanish ''Ave it!' — and with defensive, devious and downright dirty football." Clemente's teams were usually resilient, functional and robustly physical, playing a high-intensity, unashamedly 'English' game based around the bloque: two defensive midfielders screening two centre-backs and, behind them, a sweeper (famously, he once picked Miguel Ángel Nadal and Fernando Hierro for Spain in combination… in central midfield). 

In a sense, this style suited the city, a largely drab and charmless industrial sprawl (until the titanium cubist sheen of Frank Gehry's Guggenheim sprouted up, at least) centred on mining, iron and the shipbuilding that had first attracted Athletic's English founders at the end of the nineteenth century. Clemente's ascent to the dugout in 1981 coincided with the high watermark of Basque football, a period of four straight league titles — Real Sociedad had won the Primera that May, and would do so again at the end of Clemente's first season in Bilbao — and the team he built in the 1980s was as unyielding as the steel in the shipyards cleaved into the banks of the Nervión. From the cantera he took the future goalkeeping legend Andoni Zubizarreta, the full-back Santi Urkiaga, the midfielders Ismael Urtubi and Miguel de Andrés and the winger Estanislao Argote, adding them to the veterans Andoni Goikoetxea, Manu Sarabia and the skipper Dani. Above all, this team played to their strengths — the San Mamés public taking a sort of perverse pride in Clemente's 'anti-football' — and were perfectly happy to ruffle more illustrious plumage in order to win. Having come ninth in 1980-81, a respectable fourth-place finish was duly achieved in Clemente's debut season, with Barcelona coming second to Real Sociedad, having blown a five-point lead with six to play. 

As the Mundial rattled round that summer, Barcelona were still celebrating having expunged from memory their collapse in La Liga by winning the European Cup-Winners' Cup, goals from Allen Simonsen and Quini securing a 2-1 victory over Standard Liège at Camp Nou. After the tournament, they welcomed the world's greatest player, Diego Maradona, from Boca Juniors. However, after scoring with a direct free-kick on debut against Valencia and netting six goals in his first 13 games, El Pelusa ('Fluff') would have a debut European season to forget, contracting hepatitis and being sidelined for almost three months — contributing to a patchy season for Barça in which they lost home and away to Athletic (1-0 and 3-2, respectively) and slipped back to fourth in the league. They could nevertheless content themselves with a dominant but ultimately narrow 2-1 Copa del Rey victory over Real Madrid in Zaragoza, thanks to a 90th-minute header from Marcos Alonso. Their coach by then was Maradona's compatriot, César Luis Menotti, who had arrived in March that year following the sacking of former Bayern coach, Udo Lattek, largely because of the slump in form brought about by Maradona's long illness. 

While Maradona recovered — and after recovering, partied — and Barça underperformed, the main prize went to Clemente's sophomore Athletic, who edged Real Madrid by a single point (and beat Barça by six) after the merengues lost 1-0 in Valencia on the final evening while the Basques won 5-1 in Las Palmas to bag a first crown since 1956. They retained the title in Clemente's third season by beating their local rivals Real Sociedad 2-1 at San Mamés in the final game (a reverse of their 2-1 defeat at the Anoeta two years earlier when La Real themselves successfully defended their title). By then supremely confident and driven, refusing to be cowed by either of the metropolitan behemoths, in 1983-84 Athletic had pipped Real on the head-to-head rule and Barça by a single point, despite the blaugranas' somewhat pyrrhic league double over the Basques (partially avenging the previous season's results). And it was during the course of that season that the incremental morbo between Barcelona and Bilbao — simmering at least since a tackle by Goikoetxea on Bernd Schuster in December 1981, in Clemente's first game against the Catalans as coach, had left 'the Blonde Angel' with a ruptured anterior cruciate ligament, his nine months on the sidelines forcing him to sit out the World Cup — finally, and spectacularly, ignited. 

The intensification can perhaps in part be explained by the country's fraught and pestilential political atmosphere: in 1983 alone, ETA had carried out 43 assassinations. Meanwhile, in an effort to tackle militant vasquismo, Spain's new ruling socialist party, Felipe González's PSOE, had established clandestine Anti-Terrorist Liberation Groups — essentially a euphemism for death squads — that were themselves responsible for at least 27 political killings in the four years of their operation prior to being disbanded in the wake of an exposé led by the El Mundo newspaper. Two years earlier, and just a week after '23-F' — Lieutenant-Colonel Antonio Tejero's preposterously ill-conceived coup d'état of February 1981 in which he stormed the Spanish parliament on the day it was appointing the new Prime Minister, Leopoldo Calvo-Sotelo, holding it hostage for a day — Enrique Castro, 'Quini', Barça's Asturian striker, then in the midst of three consecutive Pichichi seasons, had been abducted from his home hours after a 6-0 victory over Hércules. He was held for 25 days. Although the kidnapping was ostensibly for economic rather than ideological reasons (Quini declined to press charges but Barça proceeded; the two kidnappers were sentenced to 10 years imprisonment and ordered to pay 10 million pesetas to the Asturian, who gave it to charity), it assuredly contributed to the uncertain air gripping the country. Certainly, it underlined to footballers that they were more than fair game, leading Schuster — who, with Barça's request to have all their games postponed having been rejected by the Spanish Federation, refused to play while his close friend was held captive — to hire permanent bodyguards of his own (little did he realise that it was on the field against Athletic that minders would be most needed). Against this noxious political backdrop, not only was the Spanish national flag likely to crystallize ill-will among the more politically militant Basques, so too was the Catalan senyera, which increasingly became a red-and-yellow rag to Bilbao's bullish football supporters, strongly associated as it was with the football club.

As if the atmosphere wasn't spicy enough during this era, the 1983-84 season's first league encounter between the two teams was preceded by deeply rancorous verbal sparring between the two coaches, an exchange going far beyond common-or-garden 'trash talk' and fouling the air to such an extent that the bad blood would ultimately spill over on to the pitch. Menotti, a tall, reed-thin, chain-smoking figure known in his homeland as El Flaco ('the Skinny One') had of course won the World Cup with Argentina in 1978 and as such was no stranger to operating within a climate of sporadic terrorist activity. For this was the period in which the rise of increasingly audacious ultra-leftist (and/or Peronist) armed guerrillas was unfailingly met with brutal and pitiless state-sponsored repression, an era known in Argentina as the guerra sucia ('Dirty War') that became formally consolidated into what was euphemistically called 'The Process' (El Proceso de reorganización nacional) under the military junta of General Jorge Videla (March 1976–March 1981). 

Indeed, it was this climate of political lawlessness and reprisals that led one of Menotti's illustrious successors, Johan Cruyff, to absent himself from the tournament, a decision at the time ascribed to a political boycott but which the Dutchman later admitted was born of the simple fear of being abducted, having himself been held at gunpoint in Barcelona the previous year. (The fear was not unfounded, either: the Peronist guerrilla group, the Montoneros, are reputed to have made over $100m from the extortive kidnapping of prominent public figures, with that of the Born brothers, heirs to a food processing conglomerate, in September 1974, alone bringing in $61.5m).

Employing language that one would rarely find in English — or Anglophone — football culture, the strident and loquacious Menotti dismissed Clemente's style as "authoritarian" and his team "defensive and destructive," while the Basque retorted by describing the long-haired Argentinian as "a hippy and a womaniser". Superficially, at least, this seemed to be the archetypal clash of open-minded, urbane gauchiste and narrow-minded, defensive (both psychologically and tactically) conservative, a characteristic much in evidence throughout Clemente's career. When, for instance, having somewhat contentiously selected Zubizarreta for the 1998 World Cup over Real Madrid's younger and sprightlier Santi Cañizares, the prickly Basque defended his selection by saying, "You don't invite people to dinner who you feel uncomfortable with. It's as simple as that. Zubi's my friend. End of story." As for Menotti, quite how left-wing he could have been to have spent the final seven of his nine years in charge working uncomplainingly under successive military dictatorships is anyone's guess (indeed, this is precisely the question broached by Roberto Gasparini and José Luis Ponsico's admittedly hostile book, El Director Técnico del Proceso, which, among other things, points out that, in 1982, with the Falklands-Malvinas Conflict in full swing, Menotti was photographed sharing a bear hug with General Leopoldo Galtieri at a pre-World Cup camp in Mar del Plata; that said, it's unreasonable to expect anybody to be a martyr.) 

Perhaps in anything other than a football sense, in which they were clearly antithetical, the simplicity of the dichotomy between the two would appear a little reductive — by the criteria of conscious ideological positions, certainly, if less so by unconscious personality types, where there indeed seemed a clear disparity: Clemente was unashamed to admit to being a card-carrying Basque nationalist even while coach of La Selección and had been known to speak of his people as a "raza especial(a special race: which had sufficiently fascistic connotations, it seems, for Menotti to tar him with that brush), while in 1994 Menotti would vie for the Justicialist Party's candidature for the governorship of Santa Fe Province, this being the ideologically difficult-to-pin-down party of the protean Juan Domingo Perón, which began life in the 1940s as authoritarian-populist and pro-Labour and by the 1990s, under Carlos Menem, had become a standard, centre-right neoliberal party. 

Whatever their unconscious political disposition or overt ideological persuasion, the fact that Clemente and Menotti were the best of enemies was unarguable, and this antipathy would still be nakedly apparent four years later when, prior to a clash between their new clubs, Espanyol and Atlético Madrid (with Goikoetxea in El Flaco's Atléti squad), the two would once again engage in bitter public quarrel, apparently prompted by the Argentinian's none too oblique criticism of his counterpart's somewhat negative tactic of clipping two metres from each wing before a Uefa Cup tie against Internazionale. "I shrink space through play, others shrink the field," he said, using the Argentinian Spanish verb achicar, associated as it was with his concept of the offside trap: el achique). This brought a predictably stinging response from the Basque, who called Menotti a "bluffer who gets by on jibes and metaphors" and a footballing "parasite" or "scrounger" whom "everyone in football knew" had only won a World Cup because the "president [Videla] had bought it for him," a reference to the decisive and highly contentious second-phase eliminator in 1978, when Argentina — inexplicably kicking off two-and-a-half hours after their rivals Brazil (in the parallel qualification group, both final matches had kicked off simultaneously) — knew they had to beat Peru 4-0 to make the final. They duly won by six clear goals. Rumours were rife that the junta, desperate for the vicarious legitimation of sporting success, immediately sent 35,000 tons of grain across the Andes and unfroze $50m in Peruvian credit, although they were never proven and the game is certainly not the obvious fix many have claimed. Not to be outdone, Menotti alluded to "attitudes and postures of fascist character" in Clemente, going on to suggest that these were issues that "ought to be resolved by psychiatric means" before finally invoking Freud's hypothesis that certain unconscious complexes, upon being brought to light, provoke a violent reaction in the subject: "And I don't understand Clemente's reaction, unless he admires or is envious of me," he added provocatively, and knowingly. 

If the personality of the two coaches could be said to find extension in the players and style of their sides — and indeed, in Argentina, Menotti's name is of course a byword for cavalier attacking play, menottismo, understood as an attitude more than anything concrete, being one of the fundamental stylistic poles of the nation's football and the antithesis of bilardismo, the cynical win-at-all-costs approach of his nemesis, Carlos Bilardo — then the flair in El Flaco's team came from those two mavericks: Maradona and the German wunderkind, Schuster. The symbol of Athletic's athleticism and force, meanwhile, was their uncompromising centre-back, Goikoetxea. It was the clash between 'Goiko' — an old-fashioned leñero ('chopper') who was talented enough to win 39 caps for Spain — and these two geniuses that ultimately brought the rivalry to the boil and gave it its acridity and unpleasantness, the Argentinian enganche on the receiving end of one of the most infamous tackles in football history.

The season's first encounter between Athletic and Barça took place on 24 September 1983 at the Camp Nou during the fourth round of matches, ending the week-long Catalan festival, Festes de la Mercè. Despite the champions Athletic coming into the match with a 100% record, Barça were three goals to the good as the hour-mark approached, at which point Schuster went in uncharacteristically hard on Goikoetxea, fouling him clearly and perhaps hurting him, too. There was a good deal of previous and many — including the culés who promptly began chanting the German's name in rapturous solidarity — saw this tackle as a deliberate and long-fermented act of revenge. When his anterior cruciate had been snapped in December 1981 — Goikoetxea charging from the defensive line like a rugby flanker to intercept the advancing Schuster's run and, when wrong-footed, crudely flicking out a boot at knee height — the tall, blonde 21-year-old pivote was arguably approaching the peak of his powers, having come second and third in the previous two seasons' Ballons D'Or; he never regained such heights. (It is to the consternation of many that he played the last of his 21 games for West Germany in 1984, aged just 24, after reported disagreements with the coach Jupp Derwall and senior players such as Karl-Heinz Rummenigge and Uli Stieleke.) Maradona writes in his autobiography, Yo soy el Diego, that just moments before the fateful tackle, with Goiko evidently flustered by the multitudes bellowing Schuster's name, muttering, "I'm going to kill that guy," and starting to charge about fretfully, he had told the Basque enforcer to calm down: "Take it easy, Goiko, chill out, you're losing 3-0 and will just get booked for nothing." Evidently, this had precisely the opposite effect on Goikoetxea who, goaded and listing like a bull summoning a few last drops of braveza before its spent collapse, was at once consumed by rage; pursuing the Argentinian away from goal and into no-man's land, he threw himself off the ground and into a tackle that caught Maradona halfway up the calf of his standing foot, snapping the lateral malleolus in his left ankle "like wood" while also rupturing the ligaments, an assault for which he wasn't even shown the red card — although he was subsequently handed the small matter of an 18-game ban (later reduced to six) and would have to field anonymous threatening phone calls from irate Barça supporters. (On the day that his domestic ban was rubber-stamped, he played a home European Cup tie against Lech Poznań; with Athletic trailing 2-0 from the first leg in Poland, Goiko headed the first goal in a 4-0 win, celebrating with what he called "tears of fury" streaming down his face.) 

Given that the rojiblancos were almost certain to finish the game empty-handed, as intimated by Maradona at the time, could this tackle have been the quintessential — and highly cowardly — act of 'taking one for the team,' deliberately removing the Argentinian sorcerer from the ranks of one of their chief rivals for four months? Perhaps that is too conspiratorial, for while Maradona wrote that "Goiko knew what he was doing," the Basque himself denied that there was anything pre-meditated about it. Nevertheless, it was this heinous tackle that earned him his infamous 'Butcher of Bilbao' epithet, and the degree of genuine remorse he felt for scything down the world's best player can probably be deduced from the somewhat gruesome fact that he had the boot with which he snapped the Argentine's ankle mounted, encased in glass, and proudly displayed on his living-room mantelpiece. For his part, Clemente poured petrol on the fire in the game's aftermath by casting aspersions as to the authenticity of Maradona's injury, insinuating that they ought to "wait a week" before judging how genuine it was. Idealistically, Menotti said he hoped the sacrifice would lead to an end to the violence. The rabidly madridista sports daily, Marca, ran the laconic headline Prohibido ser artista ('No Artists Allowed') and looking at the tackle now, it seems positively medieval, criminal almost. It certainly proved a decisive event in Maradona's life, for he has admitted that it was during the recuperation period that he first dabbled with cocaine. 

A little over a month later, the two teams squared up anew — without Goikoetxea and Maradona, of course — in the final of the Supercopa, which pits the previous season's La Liga and Copa del Rey winners against each other over two legs. In those days, it was not the warmly anticipated curtain-raiser it has recently become but an unloved match shoehorned into the schedule. Be that as it may, the first match in Bilbao was watched by a near-capacity 38,000, Barça running out comfortable 3-1 winners. Consequently, for the return leg, played a whole five weeks later and won 1-0 by the bilbaíno visitors courtesy of a second-minute goal from the striker Endika, only 18,000 huddled into the cavernous Camp Nou, the poor turnout more a symptom of the competition's lack of prestige at the time and the unlikelihood of an Athletic win than a reflection of any waning in the ill feeling between the clubs. The fourth meeting that season, in the return Primera fixture at the end of January, was another bruising encounter, Barcelona winning 2-1 at San Mamés to move within four points of the Basques at the top of the table. However, despite Barça powering down the home-straight with eight wins and a draw (against Valencia at home), the absence of their Argentinian talisman for such a long stretch of the season (not to mention two months without Schuster, injured just three weeks after Maradona) saw their title aspirations come up short by a single point. With Real Madrid held at home by Sevilla in the 27th jornada, the week after losing the Madrid derby, Athletic beat Real Murcia 1-0 to go top and, despite failing to win any game by more than a single goal, remained there over the final eight games to land their eighth title. 

The blaugrana, though, had one last chance for revenge when the two teams met for the fifth time that season in the final of the Copa del Rey on a damp May evening at the Santiago Bernabéu — Barça defending their trophy, Bilbao gunning for a double, both clubs having sneaked through the two-legged semi-finals on penalties (past Las Palmas and Real Madrid, respectively). An indication of the tense atmosphere and festering animosity came in a pre-match media spat between Maradona and Clemente. Maradona forgave Goiko after the game in which he was hacked down, but could never forgive the coach, even making — to put it mildly — an incredibly 'unorthodox' statement for a Barça player, practically an act of apostasy, proclaiming that he wished Real Madrid rather than Bilbao had won the title. The ever mettlesome Athletic boss retorted bluntly that Maradona was "an out-and-out fool". The tone for a predictably tetchy encounter was cemented when sections of the Basque support — outnumbering the culés by around 54,000 to 20,000 — started to whistle and shout "Qué se jodan!("Fuck them!") during a minute's silence being observed for Barcelona fans who had died in a coach accident en route to the capital. The storm was brewing. And so it was that, in front of King Juan Carlos I, this short-lived feud between arguably the country's two least monarchist clubs (witness all those with Real in their names: Madrid, Mallorca, Valladolid, Zaragoza, Betis, Gijón, Sociedad, Espanyol…) ended in one of the most disgraceful on-field brawls ever seen in top-level club football, the whole game having been studded by cynical fouls, each one contributing to the malevolent atmosphere. Schuster even responded to the barracking by lobbing missiles back into the crowd. 

The game itself was largely forgettable, containing few clear-cut chances. An early goal from Endika — smartly chest-trapping and firing home a first-time left-footed finish after Argote had returned his own poorly-cleared corner to the penalty box — paved the way for Clemente's preferred strategy of sitting back, defending deep and playing on the counter-attack, all the while denying space to Barça's twin playmakers, whom they harassed to the point of distraction with niggly fouls and stray limbs. Bilbao duly protected their lead —with relative comfort — to finish 1-0 victors, securing only the second doblete in the club's history. As the bilbaínos' bench emptied in jubilation at the final whistle, Maradona flipped, later claiming that the trigger was a V-sign from the Athletic defender José 'Chato' Núñez (with whom he had gone forehead-to-forehead in the second half after a penalty-box dribble had been abruptly terminated by a wonderfully clean tackle that caused him to tumble and led to intimations from the Basque that he had dived). At any rate, upon passing the unused Bilbao substitute Miguel Ángel Sola, who was kneeling in celebration, Maradona suddenly kneed him hard in the face, knocking him out, sparking a flurry of studs-up high-kicking, players rushing into the melee from all angles and bounding at each other like demented springboks. Maradona launched several more karate-kicks and received a blow to the thigh from — who else? — Goiko. Sola was soon stretchered from the field by the Red Cross, while Maradona, briefly isolated, was rescued from what might have been a severe pummelling by the intervention of the legendary Barça defender Migueli, who, living up to his nickname 'Tarzan', threw himself into the breach with a colossal leap and kick to the small of a rojiblanco back as all manner of people flooded the pitch: substitutes, riot police, TV crews, photographers, backroom staff, paramedics and fans. Although the initial mayhem soon subsided — some players running the gauntlet and leaving the field, others clustering in the centre circle — the overall conflagration hadn't entirely abated when Bilbao's skipper Dani received the cup from the bewildered and horrified king. Many present that day have said that it was a minor miracle that nobody was seriously injured in the brawl; it was perhaps equally perplexing that no-one was punished there and then, the referee Franco Martínez claiming not to have seen the start of the fracas. Even so, the Spanish federation later meted out heavy sanctions, including three-month bans each to Maradona, Migueli and Paco Clos from Barca, and the same to Sarabia, De Andrés and Goikoetxea from Athletic.  

This ignominious episode was both the nadir and culmination of a fleeting yet intense rivalry, a disgrace that, mercifully, produced little in the way of violence between the fans nor any long-lasting animosity between the two clubs. Having guaranteed his place in Athletic legend, Clemente guided the rojiblancos to third and fourth in the following seasons, while his second spell in charge of Athletic would end in dismissal in 1991, shortly after Cruyff's 'Dream Team' had consigned Los Leones to their heaviest ever home defeat, 6-1 (a partial and belated revenge for the fact that Barça's largest loss was a 12-1 drubbing in San Mamés at the hands of Fred Pentland's Athletic in 1932, the biggest win in the entire history of La Liga). 

With his mother having passed away, El Flaco returned to South America, coaching Peñarol of Uruguay, while Maradona, after playing just 36 La Liga games (scoring 22 goals), would never again wear the blaugrana shirt — the thought of him missing three months for a third straight season evidently too much for President Núñez — and only ventured back to Spain to play for Sevilla (ironically, under the other nemesis of Menotti, Carlos Bilardo) after seven eventful seasons in Naples. Thus it was that, with the departure of the rivalry's principal protagonists, the brief wave of morbo dissipated just as suddenly as it had arisen, both sides getting back to the bread-and-butter loathing of those villainous centrists of Madrid.